Heavy duty motor vehicles include a hydraulic power steering system in which the wheels of the steering axle of the vehicle are steered by turning a steering wheel operatively connected to a fluid motor. Turning the steering wheel operates a control valve that directs the flow of high-pressure fluid supplied from a pump or accumulator to the fluid motor and drives the motor piston. Piston movement drives an output member, such as a Pitman arm, connected to a steering linkage that in turn drives the wheels towards or away from their centered positions.
Customers of some heavy-duty motor vehicles, such as refuse trucks, often require that the truck have dual steering wheels that enable steering from either the left or right sides of the truck. Conventional dual steering wheel systems utilize “T-boxes” with miter gears that mechanically interconnect the two steering wheels on the input side of the steering system and drive a common steering shaft that operates the control valve. The miter gears and related bearings generate friction that impairs steering feel, and the mechanical linkages greatly complicate truck assembly and limit design options.
Thus there is a need for an improved hydraulic power steering system for use with motor vehicles having dual steering wheels.